Spinning element of an air-jet spinning nozzle for an air-jet spinning machine

ABSTRACT

A spinning element of an air-jet spinning nozzle for an air-jet spinning machine for producing a yarn from a sliver using an airflow. The spinning element of the air-jet spinning nozzle for the air-jet spinning machine and a corresponding air-jet spinning nozzle allows a particularly inexpensive, low-maintenance, and simple operation of an air-jet spinning machine without compromising the quality and strength of the air-jet spun yarn and without requiring frequent cleaning. This is achieved in that the spinning element has at least one fibre- and/or thread-guiding surface, an anti-adhesive coating being located on at least some sections of the fibre- and/or thread-guiding surface.

The invention relates to a spinning element of an air-jet spinning nozzle for an air-jet spinning machine for producing a yarn from a fibre band by means of an air flow as well as an air-jet spinning nozzle with an air-jet spinning nozzle spinning element.

In general, during air spinning, a fibre band is fed via a drafting system to an air-jet spinning nozzle and the outer threads of the fibre band are wrapped around an inner fibre core within a vortex chamber of the air-jet spinning nozzle by means of a vortex air flow generated by air nozzles in the region of an inlet mouth of the air-jet spinning nozzle, as a result of which the wrap fibres, which are decisive for the desired strength of the yarn, are finally formed. In principle, this can be done with fibres made of different materials, with both natural fibres such as cotton, as well as synthetic fibres such as polyester, and mixtures of natural and synthetic fibres being used.

However, when spinning polyester fibres by means of an air-jet spinning machine, it is necessary in the prior art to apply an additive into the air-jet spinning nozzle itself or on to the polyester fibres to be spun, since only by means of such an additive can it be prevented that polymer residues, polyester fibre fragments and/or finishing agents accumulate inside the air-jet spinning nozzle and thereby in particular on a surface of the spinning cone. However, such deposits considerably interfere with the air-jet spinning process and considerably worsen the spinning result and thus the yarn quality. In particular, thread breaks can then occur during the spinning process as a result of the increased friction between the surfaces of the air-jet spinning nozzle and the fibres. Furthermore, the air nozzles and additional components of the air-jet spinning nozzle become clogged by deposits, resulting in lower yarn strength and lower yarn quality of the yarn produced.

However, use of the additive also involves a number of disadvantages. On one hand, the use of the additive leads to an increase in the production costs, and on the other hand the additive remains on the air-spun yarn and will possibly have to be removed before further processing of the yarn. Additionally, due to the use of the additive corresponding components of the air-jet spinning machine must be regularly cleaned in order to remove any surplus additive deposited on the components.

The invention is based on the problem to provide a spinning element of an air-jet spinning nozzle for an air-jet spinning machine and a corresponding air-jet spinning nozzle with a spinning element which enables particularly cost-effective, low maintenance and simple operation of a workstation of the air-jet spinning machine without impairing the quality and strength of the air-spun yarn and wherein there is no necessity for frequent cleaning of the components of the air-jet spinning machine and the air-spun yarn.

According to the present invention, the problem is solved by means of a spinning element of an air-jet spinning nozzle for an air-jet spinning machine according to claim 1 and a corresponding air-jet spinning nozzle with a spinning element according to claim 11. Advantageous developments of the invention are stated in the dependent claims.

The spinning element according to the invention of an air-jet spinning nozzle for an air-jet spinning machine for producing a fibre or yarn from a fibre band by means of an air flow has at least one fibre-guiding and/or thread-guiding surface, a non-stick coating being applied to the fibre-guiding and/or thread-guiding surface, at least on sections thereof.

The air-jet spinning nozzle according to the invention has at least one spinning element according to the invention arranged inside said air-jet spinning nozzle, wherein also in particular several and/or mutually differing spinning elements according to the invention can be arranged in and/or on the air-jet spinning nozzle.

The inventors have recognised that the effect of an additive can also be achieved by means of a durable non-stick coating at least on one portion of the air-jet spinning nozzle or at least on a portion of a spinning element of an air-jet spinning nozzle respectively and in an advantageous manner an additive can then be dispensed with, so that the air-jet spinning process can be operated much more simply, more cost-effectively and with less need for cleaning. In addition, the non-stick coating advantageously leads to a reduction of air consumption, since an identical spinning result can be achieved at lower air pressure. The possibility of obtaining a greater wrap fibre angle means that higher yarn strength can also be achieved by simple means. Finally the non-stick coating allows the production speed to be increased.

An air-jet spinning machine is understood initially to mean any spinning machine which, by means of at least one air flow, interlaces fibres, in particular wrap fibres, around an internal fibre core to form a thread or yarn. The yarn-forming process takes place in the area of an air-jet spinning nozzle formed by one or more spinning elements. An air-jet spinning machine preferably has at least one workstation or spinning unit comprising an air-jet spinning nozzle, each spinning unit serving to produce a yarn from a fibre band fed to the air-jet spinning nozzle. The air-jet spinning nozzle has an inlet for the fibre band, an inner vortex chamber, one or more yarn forming or spinning elements arranged at least in sections in the vortex chamber, and an outlet for the yarn produced inside the vortex chamber. In addition, the air-jet spinning nozzle preferably has a plurality of air nozzles which open into the vortex chamber and which are particularly preferably in fluid connection with at least one air supply line, in which case during the operation of the air-jet spinning machine, compressed air provided by the air supply line flows into the vortex chamber via the air nozzles in order to produce a vortex air flow within the vortex chamber for air spinning of the fibre band into a yarn.

In the context of the present invention, a yarn or thread is a fibre bundle in which at least some of the fibres are wrapped around an inner fibre core. A yarn can also be a roving for further processing, for example by means of a ring spinning machine. The fibre band, and thus the yarn produced from it, is preferably formed at least partly, particularly preferably completely, from synthetic fibres or man-made fibres, for example polyester.

A spinning element can be an independent component, a section of a construction unit, or a functional unit involved preferably directly in the air-jet spinning process. The spinning element can be composed of a single piece or of multiple pieces. According to the invention, the spinning element is an air-jet spinning nozzle or part thereof. Also preferably, as part of the air-jet spinning process, the spinning element, at least in sections, comes into direct contact with the fibres to be spun and/or with the yarn that has just been spun. Here, the spinning element can be in particular a component of a vortex chamber and at least in sections can form the inner wall of the vortex chamber. Alternatively or additionally, the spinning element can also form part of a spinning cone and thereby can be both a part of its outer surface and/or at least a part of a extraction channel in the interior of the spinning cone.

According to the invention the spinning element has at least one fibre-guiding and/or thread-guiding surface. In it, the fibre-guiding and/or thread-guiding surface is initially each surface of the spinning element which can come into contact with the unspun fibre material and/or with the fibre material which has already been spun into a yarn before, during and after the air-jet spinning process. Preferably the fibre-guiding and/or thread-guiding surface is arranged entirely within the air-jet spinning nozzle. Particularly preferably, the fibre-guiding and/or thread-guiding surface is, at least in sections, and quite particularly preferably is arranged entirely inside the vortex chamber of the air-jet spinning nozzle, within which the unspun fibres are interlaced to form yarn.

Basically, the fibre band is the fibre material fed to the air-jet spinning process, which fibre material is preferably provided as a coherent band or bundle of fibres which are to be spun. All the fibres can be made of the same material, or the fibre band can contain fibres which are chemically different from each other. However, the fibres in the fibre band are generally not yet spun together.

The non-stick coating is initially in principle a coating of a surface to reduce the static and/or dynamic friction between the coated surface or the surface of the coating respectively and the yarn or individual fibres respectively. In this case, the non-stick coating preferably exhibits a connected and/or closed surface. Further preferably, the surface of the non-stick coating is smooth. In it, the non-stick coating can basically be provided in any material, the non-stick coating preferably comprising at least one polymer. Particularly preferably, the non-stick coating comprises a thermoplastic polymer and quite particularly preferably the non-stick coating substantially comprises a thermoplastic polymer.

In addition to the lowering of the static and/or dynamic friction, the non-stick coating preferably also leads to a hydrophobization and/or oleophobization of the surface, so preventing the adherence of water and/or oil-soluble substances. Preferably, the non-stick coating also has an antistatic effect, so that the coated surface and the fibres for spinning or the air-spun yarn respectively are not charged as a result of the friction on the surface of the spinning element, which could result in a deterioration of the spinning result.

The application of the non-stick coating can also be achieved in any manner. For example, the non-stick coating on the surface of the spinning element may be sprayed on and/or fused on. Particularly preferably, the material of the non-stick coating is applied to the surface to be coated as a powder or emulsion and subsequently particularly preferably fused with it or on to it. Also the adhesion of the non-stick coating to the surface of the spinning element can be achieved by chemical bonding and/or purely physically. In addition, a binding agent and/or adhesive may be used as well.

According to the invention at least one portion of a fibre-guiding and/or thread-guiding surface is coated with the non-stick coating. Several non-connected portions of a fibre-guiding and/or thread-guiding surface may also each exhibit a non-stick coating. Additionally, several components of the air-jet spinning nozzle may exhibit a non-stick coating on portions, or preferably on the entire inner surface inside the vortex chamber.

A preferred development of the spinning element according to the invention involves the non-stick coating having a lower coefficient of friction than the underlying material of the spinning element, by which means adherence of fibres and/or of the additive located on the fibres or on the yarn is advantageously prevented on the one hand, and better sliding of the fibres on the surface of the spinning element is achieved on the other hand. In a spinning cone in particular as a surface-coated spinning element, a higher rotational speed of the fibres on the spinning cone can advantageously be achieved. Preferably, the surface of the non-stick coating has a coefficient of friction lower by at least 10%, particularly preferably by 25% and quite particularly preferably by 50% than the material of the spinning element, particularly in the region below the non-stick coating.

To guarantee a particularly low static and/or dynamic friction between the spinning element and the fibres or yarn respectively, it is preferred that the coefficient of friction of the fibre-guiding and/or thread-guiding surface with the non-stick coating is less than 0.4, preferably less than 0.35, particularly preferably less than 0.3.

According to an advantageous development of the spinning element according to the invention, the non-stick coating is formed from a fluorinated hydrocarbon or a fluorinated hydrocarbon polymer, in particular of polytetrafluoroethylene (Teflon, PTFE) and/or from a perfluoroalkoxy alkane polymer or a perfluoroalkoxy polymer (PFA) respectively and/or from a fluorinated ethylene propylene polymer or a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) respectively. Here, the non-stick coating preferably comprises a proportion of PTFE, FEP and/or PFA of over 50% and particularly preferably of at least 90%. In addition to PTFE, FEP and/or PFA, the non-stick coating also contains further polymer material and/or additives, but preferably not more than 5% in relation to the total mass of the applied non-stick coating. Preferably, the non-stick coating has PTFE as the main component and is particularly preferably substantially comprised thereof, since PTFE typically has a coefficient of friction of around 0.25 and a friction value <0.05. The mechanically slightly softer PFA usually has a slightly lower coefficient of friction of around 0.2-0.25 and FRP has a higher strength than PFTE, but also a slightly higher coefficient of friction.

In a preferred development of the spinning element according to the invention the fibre-guiding and/or thread-guiding surface is at least a surface portion of a spinning cone and/or of a needle and/or of a pair of tweezers of an air-jet spinning nozzle, through which fibre, finishing agent and/or polymer deposits can be avoided by simple means. It is particularly preferred if the spinning element is a spinning cone and/or a needle and/or a pair of tweezers of an air-jet spinning nozzle. Also preferably, the entire fibre-guiding and/or thread-guiding surface or the entire surface of the spinning cone respectively and/or of the needle and/or of a pair of tweezers, which may come into contact with fibres and/or a yarn, is coated with a non-stick coating. Particularly preferably, however, the tip of the spinning cone around which the fibres are wrapped to form the air-spun yarn is coated with a non-stick coating.

It is particularly preferred if the spinning element is a spinning cone whose surface, in particular the fibre-guiding and/or thread-guiding surface, at least in the region of the tip, has a non-stick coating in its circumferential direction preferably over at least 10%, particularly preferably over at least 25% and quite particularly preferably over at least 50% of the length of the spinning cone running in the direction of yarn removal, and furthermore preferably over at least 10%, particularly preferably over at least 25%, along its circumferential direction. Additionally, the spinning cone may also have a non-stick coating over its entire length in the yarn removal direction and/or circumferential direction of the fibre-guiding and/or thread-guiding surface or the entire spinning cone respectively.

The fibre-guiding and/or thread-guiding surface can be arranged in any way relative to the yarn or fibre band respectively running through the air-jet spinning nozzle, wherein the fibre-guiding and/or thread-guiding surface according to an advantageous development of the invention comprising a surface surrounding the yarn and/or the fibre band. In this connection, the expression “surrounding” means that the yarn and/or fibre band inside the air-jet spinning nozzle is surrounded at least partially by the fibre-guiding and/or thread-guiding surface, the fibre-guiding and/or thread-guiding surface surrounding the yarn and/or fibre band preferably up to at least 90°, particularly preferably at least 180°, quite particularly preferably at least 270° and in particular preferably to the full extent.

It is particularly preferable for the surface surrounding the yarn and/or fibre band to comprise an inner wall of an air-jet spinning nozzle, in particular an inner wall of a vortex chamber, wherein deposits on the inner wall and in particular in the region of nozzle bore openings leading into the vortex chamber are advantageously prevented, so that the air throughput for producing the air-jet spinning yarn is maintained. Basically, only part of the inner wall of an air-jet spinning nozzle, and in particular of the vortex chamber, can be coated, wherein preferably at least the part of the inner wall exhibiting the nozzle bore openings, and particularly preferably the entire inner wall, has a non-stick coating.

In principle, the non-stick coating of the spinning element can be of any thickness and any structure. Preferably, however, the non-stick coating exhibits a layer thickness of between 2 μm and 2 mm, preferably between 5 μm and 500 μm, particularly preferably between 10 μm and 200 μm and quite particularly preferably between 10 μm and 150 μm, by which means on the one hand the surface characteristics are affected positively and on the other hand there is no change in the geometry inside the air-jet spinning nozzle resulting from the non-stick coating. In addition, the non-stick coating is of a homogeneous structure, preferably over the entire layer thickness.

In addition to the reduction of the static and dynamic friction, the non-stick coating may exhibit further functions. Particularly preferably, the non-stick coating has an anti-static surface, wherein the spinning element is suitable particularly for polymer and plastics fibres, particularly for polyester fibres, since the fibres on the plastic surface are not electrostatically charged and/or do not remain adhering to it.

An embodiment example of the spinning element according to the invention is described in more detail by reference to the drawing. In the drawing:

FIG. 1 shows a schematic perspective view of components of an air-jet spinning nozzle, including a spinning element with a non-stick coating.

In an air-jet spinning nozzle 2 shown schematically in FIG. 1 of an air-jet spinning machine, a fibre band 4 is fed from a drafting system via a delivery roller pair 10 to a vortex chamber of the air-jet spinning nozzle 2, in order to interlace the outer fibres of the fibre band 4 around a fibre core and thus to form a yarn 3.

In this, the air-jet spinning nozzle 2 exhibits a plurality of spinning elements 1 which each have a fibre-guiding or thread-guiding surface 5 respectively. One of the spinning elements 1 is a needle 9 which has a fibre-guiding surface and is arranged in the region of a fibre inlet opening of the air-jet spinning nozzle 2, while another spinning element 1 is a spinning cone 8 which in the region of its tip has a fibre-guiding and thread-guiding surface 5.

To reduce the static and dynamic friction between the spinning elements 1 and thus achieve a higher wrap fibre angle and consequently a higher yarn strength, a non-stick coating 6 is applied at least to the tip of the spinning cone 8. According to this preferred embodiment example, this non-stick coating 6 is a polytetrafluoroethylene (Teflon, PTFE) coating that is applied extensively and with a smooth surface to the material 7 of the spinning cone 8 and thereby exhibits a significantly lower coefficient of friction than the material 7 of the spinning cone 8. Alternatively to the Teflon coating, the coating according to a further preferred embodiment example may comprise a perfluoroalkoxy alkane polymer or a perfluoroalkoxy polymer (PFA) respectively or a fluorinated ethylene propylene polymer or a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) respectively or a mixture of the mentioned coatings.

In addition to at least one surface portion of the spinning cone 8, the portion of the needle 9 also coming into contact with the fibre band 4 may also have a non-stick coating 6, which preferably also consists of a fluorinated hydrocarbon or fluorinated hydrocarbon polymer, particularly polytetrafluoroethylene (Teflon, PTFE) and/or a perfluoroalkoxy alkane polymer or a perfluoroalkoxy polymer (PFA) respectively and/or a fluorinated ethylene propylene polymer or a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) respectively.

In addition to the aforementioned fibre-guiding and/or thread-guiding surfaces 5, a surface surrounding the fibre band 4 and/or the yarn 3, particularly at least one portion of an inner wall of the air-jet spinning nozzle 2 and particularly preferably an inner wall of a vortex chamber, can also have a non-stick coating 6, which quite particularly preferably exhibits the same chemical composition as the non-stick coating 6 of the spinning element or spinning elements 1.

LIST OF REFERENCE SIGNS

-   -   1 Spinning element     -   2 Air-jet spinning nozzle     -   3 Yarn     -   4 Fibre band     -   5 Fibre-guiding and/or thread-guiding surface     -   6 Non-stick coating     -   7 Material     -   8 Spinning cone     -   9 Needle     -   10 Delivery roller pair 

1. A spinning element of an air-jet spinning nozzle for an air-jet spinning machine for producing a yarn from a fibre band by an air flow, with at least one fibre-guiding and/or thread-guiding surface, wherein the at least one fibre-guiding and/or thread-guiding surface exhibits at least on portions a non-stick coating.
 2. The spinning element according to claim 1, wherein the non-stick coating has a lower coefficient of friction than underlying material of the spinning element.
 3. The spinning element according to claim 1, wherein a coefficient of friction of the at least one fibre-guiding and/or thread-guiding surface with the non-stick coating is less than 0.3.
 4. The spinning element according to claim 1, wherein the non-stick coating consists of polytetrafluoroethylene or a perfluoroalkoxy polymer or a tetrafluoroethylene-hexafluoropropylene copolymer.
 5. The spinning element according to claim 1, wherein the at least one fibre-guiding and/or thread-guiding surface is at least one surface portion of a spinning cone and/or of a needle and/or of a pair of tweezers of the air-jet spinning nozzle.
 6. The spinning element according to claim 1, wherein the spinning element is a spinning cone whose surface at least in a region of a tip thereof has at least 25% of a length of the spinning cone running in a yarn removal direction and at least 25% along a circumferential direction thereof has the non-stick coating wherein the spinning cone exhibits an inlet mouth to accept spun yarn into an extraction channel defining the yarn removal direction.
 7. The spinning element according to claim 1, wherein the at least one fibre-guiding and/or thread-guiding surface is a surface surrounding the yarn and/or the fibre band.
 8. The spinning element according to claim 7, wherein the surface surrounding the yarn and/or the fibre band is an inner wall of the air-jet spinning nozzle.
 9. The spinning element according to claim 1, wherein the non-stick coating exhibits a layer thickness of between 10 μm and 200 μm.
 10. The spinning element according to claim 1, wherein the non-stick coating exhibits an antistatic surface.
 11. An air-jet spinning nozzle for an air-jet spinning machine, with at least one spinning element arranged inside the air-jet spinning nozzle according to claim
 1. 12. The spinning element according to claim 6, wherein the surface of the spinning cone is a fibre-guiding and/or thread-guiding surface.
 13. The spinning element according to claim 8, wherein the inner wall is of a vortex chamber.
 14. An air-jet spinning machine comprising: an air-jet spinning nozzle having a spinning element for producing a yarn from a fibre band by an air flow; the spinning element including at least one fibre-guiding and/or thread-guiding surface; and a non-stick coating on at least a portion of the at least one fibre-guiding and/or thread-guiding surface.
 15. The air-jet spinning machine according to claim 14, wherein the at least one fibre-guiding and/or thread-guiding surface is at least one surface portion of at least one of a spinning cone, a needle, a pair of tweezers of the air-jet spinning nozzle.
 16. The air-jet spinning machine according to claim 14, wherein the spinning element comprises a spinning cone whose surface at least in a region of a tip thereof has at least 25% of a length of the spinning cone running in a yarn removal direction and at least 25% along a circumferential direction thereof has the non-stick coating, and wherein the spinning cone includes an inlet mouth to accept spun yarn into an extraction channel defining the yarn removal direction.
 17. The air-jet spinning machine according to claim 14, wherein the at least one fibre-guiding and/or thread-guiding surface is a surface surrounding the yarn and/or the fibre band.
 18. The air-jet spinning machine according to claim 17, wherein the surface surrounding the yarn and/or the fibre band is an inner wall of the air-jet spinning nozzle.
 19. The air-jet spinning machine according to claim 14, wherein the non-stick coating has a thickness of between 10 μm and 200 μm.
 20. The air-jet spinning machine according to claim 1, wherein the non-stick coating is antistatic. 